To: Board of Supervisors
From: John Kopchik, Director, Conservation and Development
Report Title: Green Valley Road Single-Family Residential Rezone and Minor Subdivision
☒Recommendation of the County Administrator ☐ Recommendation of Board Committee
RECOMMENDATIONS:
1. OPEN the public hearing on the Green Valley Road Rezone and Minor Subdivision project, RECEIVE testimony, and CLOSE the public hearing.
2. FIND that the Mitigated Negative Declaration (SCH 2025031276) adequately analyzes the project’s environmental impacts, that there is no substantial evidence the project will have a significant effect on the environment, and that the mitigated negative declaration reflects the County’s independent judgment and analysis.
3. ADOPT the Mitigated Negative Declaration and Mitigation Monitoring and Reporting Program for the project.
4. SPECIFY that the Department of Conservation and Development (located at 30 Muir Road, Martinez, CA) is the custodian of the documents and other materials, which constitute the record of proceedings upon which the decision of the Board of Supervisors is based.
5. ADOPT Ordinance No. 2026-04 rezoning the approximately 2-acre project site and adjacent public right-of-way from the General Agricultural (A-2) zoning district to the Single-Family Residential (R-40) zoning district (County File #CDRZ23-03271).
6. APPROVE the Vesting Tentative Map for the Project (County File #CDMS23-00005).
7. APPROVE Variances to allow a 0-foot front setback (where 25 feet is required) and an 8-foot side yard (where 20 feet is required) for construction of retaining “Wall #1” and to allow a 5-foot front setback (where 25 feet is required) for construction of retaining “Wall #3”.
8. APPROVE an exception to the requirements and regulations of County Code Title 9, County Code Chapter 96-10, for undergrounding of existing overhead utility services.
9. APPROVE the Tree Permit to allow the removal of eight (8) code-protected trees and work within the driplines of four (4) code-protected trees.
10. APPROVE the findings in support of the Project.
11. APPROVE the Project conditions of approval.
12. APPROVE the Green Valley Road Rezone and Minor Subdivision Project.
13. DIRECT the Department of Conservation and Development to file a CEQA Notice of Determination with the County Clerk.
FISCAL IMPACT:
None. The applicant has paid the necessary application deposit and is obligated to pay supplemental fees to recover any and all additional costs associated with the application process.
BACKGROUND:
The applicant is seeking approval of the Green Valley Road Rezone and Minor Subdivision Project, including Rezone, Vesting Tentative Map, and Variance and Tree Permit approvals, and an exception to the requirements and regulations of County Code Title 9 related to the undergrounding of existing overhead utility services along Green Valley Road for a development consisting of two new parcels resulting from the subdivision of an approximately 2-acre lot, one new single-family residence and retaining walls, and associated access, utility, and drainage improvements.
SITE DESCRIPTION
The subject property is an approximately 2-acre, irregularly shaped lot that is assigned two parcel numbers. The property is located at 1921 Green Valley Road in the Alamo area of the County, approximately 1/4-mile north of Stone Valley Road, approximately 1-3/4-miles northeast of I-680, and approximately 962 feet south of the Green Valley trail head with access to the Summit Trail at the base of Mount Diablo. The West Branch of Green Valley Creek is located approximately 378 feet west of the project site. Located within the foothills of Mount Diablo and situated at the bottom of a low hill that is part of a series of low ridges and small canyons to the west, the subject property has fairly steep topography rising approximately 140 feet from the eastern property line fronting Green Valley Road to the western property line, with an average slope of approximately 53 percent. The project site for a proposed residence where an existing barn is located is relatively level with slopes that are less than 15 percent in grade. The existing driveway is fairly steep and narrow and bisects the property above the barn. Nineteen mature, code-protected trees (measuring more than 6.5-inches in diameter) on the subject property and seventeen mature, non-code-protected trees in the public right-of-way along the frontage of the subject property were inventoried by the project arborist.
Developments in the surrounding unincorporated area are located within a variety of single-family residential zoning districts (R-10, R-15, R-20, R-40, or R-100), Planned Unit (P-1) districts, and General Agriculture (A-2) districts. The project site within an A-2 General Agricultural (A-2) zoning district is developed with a single-family residence, driveway, and barn. The surrounding area of Alamo is predominantly developed with single-family residences with related land uses including Monte Vista High School and Los Cerros Middle School, Monte Vista swimming pool and sports complex, and Oak Hill Park, all approximately 1/2-mile south of the project site. Nearby town centers include Alamo (e.g., Alamo Plaza) approximately 3 miles to the west and downtown Danville approximately 2 miles to the south.
PROJECT DESCRIPTION
The applicant requests a rezone of the property from A-2, General Agricultural District to R-40, Single-Family Residential district and approval of a vesting tentative map to subdivide the subject 2-acre property into two parcels, resulting in a 0.95-acre (gross) Parcel A and a 1.05-acre (gross) Parcel B, with an approximately 4,339 square-foot private access and utility easement (PAUE) approximately 25 feet in width on proposed Parcel B.
Improvements to the existing driveway within a new private access and utility easement (PAUE) include widening the driveway where it connects to Green Valley Road to approximately 20 feet and repaving portions of the driveway. An improved and widened driveway to a new residence on proposed Parcel B would split from the PAUE. New development proposed for Parcel A consists of the installation of two bioretention filters for stormwater control. No other changes or improvements are proposed for Parcel A where an existing residence would remain.
Other site improvements include three bioretention filters, a concrete ditch, and trench inlets/drains for stormwater control and drainage. Six retaining walls ranging between zero and nine feet in height are proposed. The applicant has requested variances to the requirements of the R-40 zoning district for the construction of two of the retaining walls that would be over three feet in height located on Parcel ‘B’:
• 0-foot front setback (where 25 feet is required) and 8-foot side yard (where 20 feet is required) for “Wall No. 1”; and,
• 5-foot front setback (where 25 feet is required) for “Wall No. 3”.
The applicant has also requested an exception from the requirements of Title 9, Chapter 96-10, of the County Ordinance Code related to the undergrounding of existing overhead utility services along the subject property’s Green Valley Road frontage. Water, sewer, electrical, and other utilities extending to the proposed residence on Parcel B would be installed underground. Trenching for those utilities, as well as drainage improvements, would be performed as part of grading. It is anticipated that the project will entail ±330 cubic yards (CYS) of cut and ±540 CYS of fill for a net 210 CYS of grading for site and residential improvements.
The applicant also requests approval of a tree permit for the removal of code-protected trees including three valley oaks, one coast live oak, three coast redwoods, and one ash (trees #106 through #113), and to allow work within the driplines of code-protected trees including one valley oak (tree #120) and three coast live oaks (trees #103 through #105) for the demolition of an existing barn, construction of retaining walls, grading, site/drainage improvements, and construction of a new residence on proposed Parcel B. As designed, the new single-family residence on Parcel B would be a 3,496-square-foot, two-story home with a 553-square-foot garage, 315-square-foot main floor deck, and 383-square-foot lower floor concrete patio.
COUNTY PLANNING COMMISSION
The County Planning Commission considered the project at a noticed public hearing on December 10, 2025. Following a presentation from staff, a presentation from the applicant, and considering public comments, the Commission voted 5-1 to recommend that the Board approve the project as recommended by staff. The Commission referred the vesting tentative map to the Board and recommended that the Board approve the rezoning, variances, exceptions, and tree permit for the project.
CALIFORNIA ENVIRONMENTAL QUALITY ACT (CEQA)
A CEQA Initial Study was prepared indicating that, with mitigations, the project would not result in any significant environmental impacts. The proposed rezone, two-lot minor subdivision, grading and site improvements, and development of proposed Parcel B with a new single-family residence may affect the quality of the environment. However, the impacts would be reduced to less than significant levels with the adoption of the recommended mitigation measures as specified in the pertinent sections of the MND, including biological resources, cultural and tribal cultural resources, geology and soils, and wildfire.
Pursuant to Section 15073 of the California Environmental Quality Act, an Initial Study and Mitigated Negative Declaration (MND) for the proposed project was posted for public review on March 25, 2025. The public comment period for accepting comments on the adequacy of the environmental analysis in the draft MND extended from March 26, 2025, through April 24, 2025. During that time three comment letters were received from the California Department of Toxic Substances Control, the East Bay Municipal Utility District (EBMUD), and David J. Bowie on behalf of the Kimberwicke Court neighborhood.
Staff has prepared a Final IS/MND for the project, included as an attachment to this report, with staff-initiated text changes, either to provide additional clarifying information or to correct typographical errors. None of the text changes are the result of any new avoidable, significant effect, nor do they alter the effectiveness of any mitigation included in the pertinent section. None of the mitigations identified in the IS/MND circulated on March 25, 2025, have been revised and no new mitigations have been added. A Final Mitigation Monitoring and Reporting Program (MMRP) was prepared based on the mitigation measures recommended in the MND. It is the finding of CDD staff that the mitigation measures identified within the MND would adequately mitigate project impacts to less than significant levels or lower. If approved, the mitigation measures identified within the Final MND and MMRP would apply to the project as Conditions of Approval.
STAFF ANALYSIS AND DISCUSSION
A. General Plan
On November 5, 2024, the County Board of Supervisors adopted the Contra Costa County 2045 General Plan. The subject Minor Subdivision and Rezoning applications were deemed “complete” for processing on October 7, 2024. Therefore, the County General Plan 2005-2020 applies and is cited throughout the Initial Study.
Land Use Designation: The project site was located within a Single-Family Residential-Low Density (SL) General Plan land use designation of the 2005-2020 General Plan. This designation allowed between 1.0 and 2.9 single-family units per net acre. The proposed single-family residence on Parcel A and structures that are accessory to residential use are consistent with the uses allowed within this designation. The two-lot minor subdivision would result in a density of approximately 1 unit per net acre, which is within the range of units allowed. Thus, the proposed subdivision of land will not alter or conflict with the density or result in more residential units than is allowed for the project site. The project proposes the rezone of the subject property from A-2, General Agricultural District to R-40, Single-Family Residential which is consistent with the SL General Plan land use designation.
Pursuant to the new County General Plan Envision 2045 adopted by the Board of Supervisors on November 5, 2024, the subject property is now located within the RVL, Residential Very Low-Density land use designation with a density of less than or equal to 1 unit per acre. Although it does not apply to the subject applications, the RVL designation would apply to future applications for the subject property. The RVL designation is appropriate for transitions between urban development and agricultural/rural areas and for constrained sites where reduced densities are justified. Typical development in RVL includes detached single-family units on lots that are approximately 1 acre or larger. The R-40 zoning district is also consistent with RVL. The proposed project that would result in two parcels approximately 1 acre each and one new single-family residence on a lot located in a transitional area between urban development to the north, south, and east and open space/park land to the west is also consistent with this designation and would not conflict with the density or result in more residential units that is allowed for the project site in RVL.
Specific Geographic Area Policies: General Plan Policies 3-115 to 3-125 are specific to the guidance of uses and development for the Alamo-Diablo-Blackhawk areas of the County. Policies 3-115, 3-116, 3-122, and 3-124 are applicable to residential development or rezoning within the Alamo area. The project is consistent with Policies 3-115 and 3-116 that are intended to promote the unique single-family residential character of this area of Alamo while also maintaining the rural character of the area pursuant to Policy 3-124. The project to rezone the property from an A-2 district to an R-40 district is consistent with Policy 3-122 ensuring that when rezoning, the appropriate single-family residential districts R-20, R-40, R-64, R-100, and P-1 Planned Unit District are included.
Conservation Element: The Conservation Element of the General Plan lists three overall conservation goals (8A-8C) intended to preserve and protect the ecological and natural resources in the County and to achieve a balance of uses of the County’s natural and developed resources to meet the social and economic needs of the County’s residents. The project site is not located within an area of known ecological sensitivity (Figure 8-1, County General Plan) and the project does not affect any known natural resources. Through the implementation of mitigation measures identified in the Final IS/MND prepared for the project, air quality, biological, geological, or cultural resources in Contra Costa County would not be significantly affected.
B. Zoning
Rezoning and Consistency with R-40 Zoning District: The project proposes to rezone the site from A-2, General Agricultural District to R-40, Single-Family Residential District. The proposed zone change from A-2 to R-40 is consistent with lots in the surrounding area which are designated with a variety of residential, Planned Unit (P-1), and agricultural districts, within an underlying SL General Plan land use designation. The proposed Vesting Tentative Map identifies two new residentially zoned lots.
The standards of the R-40 zoning district require lots to have a minimum lot area of 40,000 square feet, a minimum 140-foot average width, and a minimum 140-foot depth. As proposed, the dimensions of the resultant parcels will comply with the minimum lot area, width, and depth standards for the R-40 zoning district. The R-40 district requires a 25-foot front setback for primary and accessory buildings or structures, a 20-foot side yard with a 40-foot side yard aggregate for primary buildings, and a 15-foot side yard. R-40 allows a 3-foot side yard for accessory structures with a minimum 75-foot front setback. The R-40 district requires a 20-foot other setback for corner lots which is also applicable to access easements. Setbacks on lots that are larger than 40,000 square feet are measured from property lines and not the edge of existing or proposed access easements (County Code section 82-4.244(d)). Therefore, although there is a proposed access easement, the “other” setback for proposed Parcel B does not apply. As designed, the proposed residence for Parcel B is consistent with the minimum front setback, rear yard, side yard, side yard aggregate, and maximum building heights.
The applicant has requested variances from the standards to allow a 0-foot front setback and an 8-foot side yard for retaining Wall #1 and to allow a 5-foot front setback for retaining Wall #3. Pursuant to County Code Section 84-16.1602, variances may be granted to modify the provisions in the R-40 district. Staff believes evidence in the record supports findings to allow the variances for reduced setbacks and a reduced side yard for retaining walls over three feet in height due to the steep topography of the subject property and the need to widen and shore up the existing driveway for safe ingress and egress and improved fire apparatus access. In addition, the use of a shared driveway minimizes the number of curb cuts on Green Valley Road. The proposed two-lot minor subdivision project and proposed residential improvements are consistent with the permitted residential land uses within the R-40 zoning district, and the R-40 zoning district is consistent with the underlying SL General Plan land use designation. Therefore, the project is consistent with the R-40 zoning district. Specific findings supporting approval of the requested variances are included in the attached Project Findings.
Tree Permit: Pursuant to the County’s Tree Protection and Preservation Ordinance (County Code Chapter 816-6), a number of mature trees on the subject property are considered to be code-protected due to their size and their presence on a property that is further subdividable if the requested rezone to an R-40 zoning district is approved. The County’s Tree Preservation and Protection Ordinance is intended to provide for the protection of trees on private property through contingency restitution should altered trees be damaged or removed, while allowing for reasonable enjoyment of private property rights and development. When protected trees are removed, the Ordinance is intended to provide for restitution through the planting of new trees.
If granted, the proposed tree permit would allow for the for the removal of eight code-protected trees (three valley oaks, one coast live oak, three coast redwoods, and one ash with a combined diameter of 149 inches) and would also allow for work within the driplines of four code-protected trees (one valley oak and three coast live oaks with a combined diameter of 79 inches) for anticipated grading, trenching, and construction activities as part of the proposed project on the subject property, primarily on proposed Parcel B. Staff believes evidence in the record supports findings to grant approval of a tree permit. The project is conditioned to require the applicant to plant replacement trees for the removed trees, to ensure the protection of trees intended to be preserved, and to deposit securities to ensure these measures are implemented. Therefore, the proposed project is consistent with the County’s Tree Protection and Preservation Ordinance. Specific findings supporting approval of the requested tree permit are included in the attached Project Findings
C. Traffic and Circulation: The project has access from Green Valley Road, a County maintained road. The Green Valley Road frontage features a curb that has been partially buried in some locations along its length at places by the elevated earthen shoulder. At this location, Green Valley Road is 30 feet wide within a 60-foot right-of-way and no right-of-way dedication is necessary for this project. The site plan proposes to remove and replace the existing driveway onto Green Valley Road. The new and wider driveway will provide direct access to the proposed residence and branch onto the existing drive that is to remain. The project is conditioned to require the applicant to relinquish abutter’s rights of access along the frontage of Green Valley Road, with the exception of the new driveway access.
D. Underground Utilities: Chapter 96-10 of the County Ordinance Code requires all existing and new utility distribution facilities to be installed underground. This requirement applies to the existing overhead lines along the site’s Green Valley Road frontage. The applicant has requested an exception from the requirement applicable to the existing overhead lines along the site’s Green Valley Road frontage. Staff of the County Public Works Department indicated that they would not be averse to the granting of the exception related to existing overhead utilities considering the character of the area and the scope of this project. The required findings for the request for exception pursuant to Chapter 92-6 have been provided and are included as part of the attached Findings. Condition of approval #56 has been modified since the County Planning Commission hearing to clarify, but not change, the exception in that it applies only to the undergrounding of existing, overhead utilities. The applicant would still be required to install any new utility extensions underground.
E. Drainage/Stormwater Management and Discharge Control: Division 914 of the County Ordinance requires that all storm water entering and/or originating on this property to be collected and conveyed, without diversion and within an adequate storm drainage system, to an adequate natural watercourse having a definable bed and banks or to an existing adequate public storm drainage system which conveys the storm water to an adequate natural watercourse. Based on County elevation data, runoff flows eastward towards Green Valley Road. Submitted plans show that proposed modifications to grading and drainage infrastructure are confined to Parcel B. Stormwater infrastructure proposed for Parcel B will tie into three separate curb inlets along Green Valley Road. A Stormwater Control Plan (SWCP) is required for applications that will create and/or redevelop impervious surface area exceeding 5,000 square feet in compliance with the County’s Stormwater Management and Discharge Control Ordinance (§1014) and the County’s Municipal Separate Storm Sewer System (MS4) National Pollutant Discharge Elimination System (NPDES) Permit. This project proposes approximately 11,000 square feet of impervious surface with the minor subdivision application, which is above the threshold for requiring submittal of a SWCP. A preliminary SWCP was submitted with the application and was considered adequate for deeming the subject applications complete for processing. The property is located within unformed Drainage Area 59. There is currently no fee ordinance adopted by the Board of Supervisors for this area. The project is conditioned to require the applicant to comply with all applicable drainage and stormwater management requirements.
CHILDREN'S IMPACT STATEMENT
None. This project is a rezoning of a property and two-lot subdivision with construction of a new residence, and variances to side yards and setbacks for the construction of accessory structures.
CONCLUSION AND STAFF RECOMMENDATION
The proposed project is consistent with applicable policies and standards of the General Plan and zoning code. In addition, an environmental analysis of the project was completed and found that the proposed project would not have a significant impact on the environment with the incorporation of specific mitigations. Staff recommends approval of the Green Valley Road Rezone and Minor Subdivision project, based on the attached findings and subject to the attached conditions of approval.
CONSEQUENCE OF NEGATIVE ACTION:
If the Board were to deny the project, the property owner would not be allowed to subdivide the property or construct driveway improvements or the new residence on proposed Parcel B.